问题
I am new to Prolog and noticed that \' and \" give different behavior, but am curious as to why. Specifically, when loading a file, ?- [\'test1.pl\']. works, while ?- [\"test1.pl\"]. doesn\'t.
回答1:
Single quoted items are always atoms.
The meaning of double quotes depends on the Prolog flag double_quotes:
atom —
with this value "a" = a. Nowadays, this is rarely used. But you will find Prolog books where ["abc.pl"] is written.
codes —
a list of character codes. This is frequently the default, but it leads to very unreadable answers like
?- set_prolog_flag(double_quotes,codes).
true.
?- phrase(("Ja tvoi ",("sluga"|"rabotnik"),"!"), Satz).
Satz = [74,97,32,116,118,111,105,32,115,108,117,103,97,33] ;
Satz = [74,97,32,116,118,111,105,32,114,97,98,111,116,110,105,107,33].
Even worse, if you use characters beyond ASCII:
?- phrase(("Я твой ",("слуга"|"работник"),"!"), Satz).
Satz = [1071,32,1090,1074,1086,1081,32,1089,1083,1091,1075,1072,33] ;
Satz = [1071,32,1090,1074,1086,1081,32,1088,1072,1073,1086,1090,1085,1080,1082,33].
chars
— a list of one-char atoms. See this for more about it.
?- set_prolog_flag(double_quotes,chars).
true.
?- phrase(("Ja tvoi ",("sluga"|"rabotnik"),"!"), Satz).
Satz = ['J',a,' ',t,v,o,i,' ',s,l,u,g,a,!] ;
Satz = ['J',a,' ',t,v,o,i,' ',r,a,b,o,t,n,i,k,!].
?- phrase(("Я твой ",("слуга"|"работник"),"!"), Satz).
Satz = ['Я',' ',т,в,о,й,' ',с,л,у,г,а,!] ;
Satz = ['Я',' ',т,в,о,й,' ',р,а,б,о,т,н,и,к,!].
This notation gives more readable answers. It can be even more compactly displayed since the double quote notation can be used for printing any list of one-char atoms. There is library(double_quotes) for SICStus and SWI.
?- use_module(library(double_quotes)).
true.
?- phrase(("Ja tvoi ",("sluga"|"rabotnik"),"!"), Satz).
Satz = "Ja tvoi sluga!" ;
Satz = "Ja tvoi rabotnik!".
?- phrase(("Я твой ",("слуга"|"работник"),"!"), Satz).
Satz = "Я твой слуга!" ;
Satz = "Я твой работник!".
If you have difficulties installing double_quotes.pl as a library, simply put it into the directory of your other Prolog files and say: use_module(double_quotes).
回答2:
Strings in Prolog are written in single quotes. Terms written in double quotes are immediately converted to a list of character codes.
?- write('sdf').
sdf
true.
?- write("sdf").
[115, 100, 102]
true.
来源：https://stackoverflow.com/questions/8264699/what-is-the-difference-between-and-in-prolog